THE FILLER CAP

Rotorua Morning Post, Volume 2, Issue 296, 9 August 1932, Page 7

THE FILLER CAP

ATTENTION NECESSARY. The rear petrol tank fitted with either pump or autovac feed to the carburetter demands a form of attention that is somewhat new in uplceep processes to a great many drivers, even. those with many years' experience. That is to say, it is highly important that the small air vent-hole in the filler eap should be kept clear by occasional probing to remove the mud and dust that tend to choke it. A bloeked or partially choked vent-

hole may he the cause of erratic running of the engine, particularly when there is need to run the latter at high speed and full throttle, as in climbing steep hills. Air cannot then enter the tank fast enough to take the place of the petrol that should issue to the carburetter, and what is known as "petrol stravation" occurs. Popping in the carburetter is sometimes a symptom. With autovac feed the result of a choked vent-hole may he far more serious, for if air cannot enter the tank while the engine is running an intense vacuum is set up inside it, representing at its worst a pressure of roughly 141b per square inch from every direction upon the whole of the •exterior surface, or nearly half a ton ip all in the case of quite a small tank. The ultimate effect is that the tank is unable to withstand the stress and collapses, conoertina fashion.